Question

Loop rules: (picture attached) I am utterly confused. So current doesn't change when it sequence, but it does when in parallel? How do I calculate current for each path. Also how do I calculate current before it has gone through any resistors?

Answer 1

first bit first....combine all the resistors to find the current leaving the battery



where in parallel you know that \(\dfrac{1}{R_{23}} = \dfrac{1}{R_2} + \dfrac{1}{R_3}\)

then add \(R_1\) and \(R_{23}\) for total resistance in circuit

Answer 2

ok the total resistance is 111k Ohms

Answer 3

Referring to your question, "Also how do I calculate current before it has gone through any resistors?" Get acquainted with Ohm's Law. You will find that resistance will need to be considered when you calculate current (as well as voltage) I (current) = E (voltage) divided by R (resistance) As your studies progress, you will learn how resistors associated with the circuit in question will be dealt with as shown in IrishBoy123 post above.

Here is some tips with regard to this circuit. Tip 1. When resistors are connected in parallel as R2 and R3 are in this circuit, their combined resistance will be less than the smallest resistor. In this case, the effective resistance will be less than 1K.

Tip 2. For this circuit, the current through R1 is equal to the total current which will then divide thru R2 and R3, with the larger value flowing thru the lowest resistor value in the parallel network (in this case R3)

Answer 4

Using those tips you can readily see that the total resistance as seen by the battery will be less than 11K. How did you get 111K ??

Answer 5

Do you see that the total resistance is the sum of R1 and the parallel equivalent of resistors R2 and R3?

Answer 6

tacotime it is "crunch" time. Do you see that the estimated total resistance of this circuit will be less than 11K Ohms

Answer 7

I didn't notice that the equation was 1/R. Give me a second to recalculate

Answer 8

Ok I now have 10000.00101 as my total resistance It doesn't look right...

Answer 9

Wait I did it wrong again. The resistor in parallel has to be inverted. arg

Answer 10

Ok I now have 10990 Ohms. That is my final answer.

Answer 11

O.K. that will make a big difference in your results. I have to go on an errand.You are on the correct path. The combined resistance of R2 and R3 in parallel is about 990 Ohms or 0.99 K Ohm add this to the 10 K will give you about 10.99 K as your total resistance. Yessss! you got the total resistance. Good luck with you studies.

Answer 12

You now can calculate the total current thru R1 and how it divides with most going thru R3 and remainder thru R2 where it recombines and returns to the battery. Have a nice day.

Answer 13

Thank you so much radar and IrishBoy123. Hopefuly there is someone else on today that can help me...
I don't really understand what the total resistance has to do with calculating the current. Am I supposed to figure out what percent of the resistance each resistor is contributing or something?

Answer 14

Well the total current is \[9.099*10^{-4}\]

Answer 15

I think IR1 = 9.099*10^-4, IR2 = 9*10^-9, and IR3 = 9.1*10^-7
Can any one tell me if this is right?

Answer 16

Yes, total current is correct, you need to use the proper units. It is more convenient to state the total current in milliamps. (a milliamp is 1/1,000 of an Amp or 10^-3) Your answer could now be stated as 0.9099 milliamp.
The sum of the currents thru R2 and R3 must equal to that (total current)
Here is a good link with a neat slide show explaining the current divider rule.:
https://www.wisc-online.com/learn/career-clusters/stem/dce3502/current-divider-rule-cdr

For this case, you have already calculated the total current. Also, you have already determined the effective resistance of the parallel R2 & R3 circuit. I want to figure the current thru R3 (it will have the most)
IR3 will be:

Answer 17

I believe your figures differ from that you have compare them with the answer I have:
IR3 = 9 10^-4 Amp
IR2 = .099 10^-4 Amp

Note when added you would get 9.099 10^-4

Answer 18

I have no clue sorry but I have to turn this in.